It is a well known fact that an air-air heat exchanger for cooling electrical cabinets generally consists of a plate pack arranged in such a way as to obtain two separate circuits for hot air and cooling air respectively.
The latter eliminates the heat content of the former in a relatively short space of time in relation to the mass flows and the surface area of contact between the fluids and said plate pack.
As the kinetic contribution of the fluid is a determining factor in guaranteeing efficient heat exchange, both circuits are often equipped with a respective means, for example a fan, of rapidly moving the air.
The plate pack is housed inside a casing, usually of metal, positioned next to the metal cabinet to be cooled and in communication with the interior of said cabinet in such a way as to eliminate heat and thus cool the air present in the cabinet.
According to an embodiment known in the art, the plate pack is formed from a single roll of sheet metal, usually aluminium, which is unrolled and then folded into an “accordion” configuration in such a way as to create a number of passages, further circumscribed by the inner surfaces of the casing and strips of insulating material. One problem with this embodiment is that the sheet metal has a flat surface and heat exchange is thus relatively low.
This can be compensated for by increasing the flow rate of the fluid, but this results in considerable energy dispersion due to localised pressure drop in relation to the square of its speed.
Also known in the art is the use of corrugated plate packs offering a higher exchange surface area for the same longitudinal dimensions.
One disadvantage of this technique is that its use is limited to packs consisting of a number of separate superimposed sheets, without them being folded into an “accordion” configuration by unrolling the sheet metal from a roll, as the folding operation would induce longitudinal tension and thus tend to reduce the curvature of the corrugations.
In addition, it is difficult to fold the sheet metal in correspondence to the corrugations and relatively thick material must therefore be used.
A further problem is that in an air-air heat exchanger made from flat sheet metal, the intake and outlet are usually opposite each other on the diagonal of the casing.
The air thus tends to cross the heat exchanger following the shortest possible route, excluding peripheral parts of the casing from the heat exchange process and consequently drastically reducing efficiency.